LDMOS (Lateral Diffused Metal Oxide Semiconductor) devices are widely used for high breakdown voltage, high current and good thermal performance in many applications including notebook, server, and DC/DC converter.
A LDMOS device comprises a well region 16, a drain pickup region 11, a source region 12, a gate 13, a body region 14, and a body pickup region 15 as shown in FIG. 1. Persons of ordinary skills in the art should know that the well region 16 is also referred as the drain drift region. For performance and cost reasons, many modern applications require smaller power devices in a smaller package. Much focus has been placed on drain engineering that includes RESURF (Reduced Surface Field), graded doped drain. Another area of focus is on making source region smaller. As shown in FIG. 1, a source/body region consists of the body pickup region 15 in the center and the source region 12 located on both sides of the body pickup region 15, which form an N+/P+/N+ region. Reducing the N+/P+/N+ region would result in a smaller source region. But usually the minimum area of the N+/P+/N+ is limited by the photo-masking equipment's capability.